JP2009024520A - Controller for internal combustion engine having variable valve train - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a controller for an internal combustion engine having a variable valve train capable of excellently preventing any fogging of an ignition plug and reducing the cylinder wet amount while maintaining fuel atomization effect using the inspiratory flow rate when performing the retarded opening control of an intake valve. <P>SOLUTION: The controller has an intake variable valve system 34 capable of changing the opening timing and the lift speed of an intake valve 30. During the cold start of an internal combustion engine 10, the intake valve retarded opening control for retarding the opening timing of the intake valve 30 from the intake top dead center is executed for promoting the fuel atomization. While performing the intake valve retarded opening control, the intake valve 30 is controlled so that the lift amount in the section from the opening timing of the intake valve 30 to the predetermined crank angle is higher in comparison with the lift curve longitudinally symmetric with the maximum lift position as the reference under the condition of the same operating angle. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an internal combustion engine control device including a variable valve mechanism.

  Conventionally, for example, Patent Document 1 discloses a valve timing control device for an internal combustion engine that includes a variable valve mechanism that makes the valve timings of an intake valve and an exhaust valve variable. In this conventional control device, when the internal combustion engine is cold-started, intake valve delay opening control is performed to delay the opening timing of the intake valve after the intake top dead center. According to such control, fuel atomization can be promoted by utilizing the improvement in the intake air flow velocity.

  In addition, in the above-described conventional control device, the closing timing of the exhaust valve is delayed from the closing time of the normal time so that the fuel flowing into the cylinder does not adhere to the exhaust valve and its periphery.

JP 2005-248766 A Japanese Patent Laid-Open No. 9-256891

  According to the above-described conventional control device method, as described above, by performing the control to delay the closing timing of the exhaust valve together with the intake valve delay opening control, the in-cylinder negative pressure when the intake valve is opened is reduced to the atmospheric pressure side. Thus, the instantaneous intake air flow velocity when the valve is opened can be suppressed. However, with such a conventional technique, the effect of fuel atomization by the slow opening control of the intake valve is reduced with the suppression of the intake flow velocity at the time of valve opening.

  The present invention has been made to solve the above-described problems, and prevents ignition plug fogging while maintaining the effect of atomizing the fuel using the intake air flow velocity when the intake valve is slowly opened. Another object of the present invention is to provide a control device for an internal combustion engine including a variable valve mechanism that makes it possible to satisfactorily reduce the amount of cylinder wet.

The first invention includes a variable valve mechanism that can change at least the opening timing and the lift speed of the intake valve;
An intake valve delay opening control means for controlling the variable valve mechanism to perform an intake valve delay opening control for retarding the opening timing of the intake valve from the intake top dead center;
The intake valve slow opening control means has a higher lift amount in a section from the opening timing of the intake valve to a predetermined crank angle, compared to a lift curve that is symmetric with respect to the maximum lift position under the same operating angle condition. Thus, the intake valve is controlled.

The second invention further comprises information acquisition means for acquiring environmental temperature information of the internal combustion engine and / or information on fuel volatility in the first invention,
The intake valve slow opening control means variably changes the lift amount in a section from the opening timing of the intake valve to the predetermined crank angle based on the environmental temperature information of the internal combustion engine and the information on fuel volatility. It is characterized by controlling.

Further, the third invention provides a variable valve mechanism that can change at least the opening timing and the lift speed of the intake valve;
An intake valve delay opening control means for controlling the variable valve mechanism to perform an intake valve delay opening control for retarding the opening timing of the intake valve from the intake top dead center;
The intake valve slow-opening control means is configured such that the absolute value of the lift speed in at least a part of the first half section from the maximum lift position is the absolute value of the lift speed in the second half section from the maximum lift position. The intake valve is controlled to be larger than the value.

The fourth invention further comprises information acquisition means for acquiring environmental temperature information of the internal combustion engine and / or information on fuel volatility in the third invention,
The intake valve slow-opening control means is based on the environmental temperature information of the internal combustion engine and / or the information on fuel volatility, and the at least a part of the first half of the section from the maximum lift position in the section. The lift speed is variably controlled.

  In a fifth aspect based on any one of the first to fourth aspects, the intake valve slow-opening control means controls the intake valve so that the maximum lift position comes near 90 ° CA after the intake top dead center. It is characterized by controlling.

  According to a sixth invention, in any one of the first to fifth inventions, the variable valve mechanism is a mechanism capable of electrically rotating a cam for driving an intake valve around a camshaft. .

  According to the first aspect of the present invention, the period during which the valve passage flow rate exhibits an excessive value at the initial stage of valve opening while maintaining the instantaneous valve passage flow rate improvement effect at the initial stage of opening the intake valve by the intake valve slow opening control. Can be shortened. As a result, it is possible to reduce the flow of intake air toward the spark plug and the vicinity of the exhaust valve while maintaining the fuel atomization promoting effect satisfactorily. For this reason, it is possible to satisfactorily prevent fogging of the spark plug while maintaining the fuel atomization promoting effect well, and the amount of fuel adhering to the cylinder wall on the exhaust side (so-called cylinder wet amount) is good. It becomes possible to reduce it.

  According to the second aspect of the invention, a good balance between the effect of promoting atomization of fuel and the effect of reducing the amount of cylinder wet, etc. is achieved based on information on the volatility of the fuel used and / or the environmental temperature of the internal combustion engine. be able to.

  According to the third aspect of the present invention, the period during which the valve passage flow rate exhibits an excessive value at the initial stage of valve opening while maintaining the effect of improving the instantaneous valve passage flow rate at the initial stage of valve opening of the intake valve by the intake valve slow opening control. Can be shortened. As a result, it is possible to reduce the flow of intake air toward the spark plug and the vicinity of the exhaust valve while maintaining the fuel atomization promoting effect satisfactorily. For this reason, it is possible to satisfactorily prevent fogging of the spark plug while maintaining the fuel atomization promoting effect well, and the amount of fuel adhering to the cylinder wall on the exhaust side (so-called cylinder wet amount) is good. It becomes possible to reduce it.

  According to the fourth aspect of the present invention, a good balance between the effect of promoting atomization of fuel and the effect of reducing the cylinder wet amount is achieved based on information on the volatility of the fuel used and / or the environmental temperature of the internal combustion engine. be able to.

  According to the fifth aspect of the invention, the lift amount of the intake valve can be effectively increased in the vicinity of 90 ° CA after the intake top dead center where the valve passage flow velocity is most likely to be highest as the piston speed increases. This makes it possible to effectively shorten the period during which the valve passage flow rate shows an excessive value.

  According to the sixth aspect of the present invention, as the variable valve mechanism controlled by the intake valve delay opening control means, the mechanism for electrically rotating the cam for driving the intake valve around the camshaft is used. It is possible to achieve a good effect according to the invention.

Embodiment 1 FIG.
[System configuration]
FIG. 1 is a diagram for explaining a configuration of an internal combustion engine 10 according to a first embodiment of the present invention. The system of this embodiment includes an internal combustion engine 10. Here, it is assumed that the internal combustion engine 10 is an in-line four-cylinder engine. A piston 12 is provided in the cylinder of the internal combustion engine 10. A combustion chamber 14 is formed in the cylinder of the internal combustion engine 10 on the top side of the piston 12. An intake passage 16 and an exhaust passage 18 communicate with the combustion chamber 14.

  An air flow meter 20 that outputs a signal corresponding to the flow rate of air sucked into the intake passage 16 is provided in the vicinity of the inlet of the intake passage 16. A throttle valve 22 is provided downstream of the air flow meter 20. The throttle valve 22 is an electronically controlled throttle valve that can control the throttle opening independently of the accelerator opening. In the vicinity of the throttle valve 22, a throttle sensor 24 for detecting the throttle opening is disposed.

  A fuel injection valve 26 for injecting fuel into the intake port of the internal combustion engine 10 is disposed downstream of the throttle valve 22. A spark plug 28 is attached to the cylinder head of the internal combustion engine 10 so as to protrude from the top of the combustion chamber 14 into the combustion chamber 14. The intake port 16a and the exhaust port are respectively provided with an intake valve 30 and an exhaust valve 32 for bringing the combustion chamber 14 and the intake passage 16 or the combustion chamber 14 and the exhaust passage 18 into a conductive state or a cut-off state.

  The intake valve 30 and the exhaust valve 32 are driven by an intake variable valve mechanism 34 and an exhaust variable valve mechanism 36, respectively. The detailed configuration of these variable valve mechanisms 34 and 36 will be described later with reference to FIGS. Further, an A / F sensor 38 for detecting the exhaust air-fuel ratio at that position is disposed in the exhaust passage 18.

  The system shown in FIG. 1 includes an ECU (Electronic Control Unit) 40. In addition to the various sensors described above, the ECU 40 includes a crank angle sensor 42 for detecting the engine speed, an accelerator opening sensor 44 for detecting the accelerator opening PA, and a cooling water temperature sensor for detecting the engine cooling water temperature. 46 and an outside air temperature sensor 48 for detecting the outside air temperature are connected. The ECU 40 is connected to the various actuators described above. The ECU 40 can control the operating state of the internal combustion engine 10 based on the sensor outputs.

  Further, the system of the present embodiment is a system (a so-called flexible fuel vehicle (FFV)) that is supplied with a plurality of fuels such as gasoline and ethanol and can operate the internal combustion engine 10 with any fuel. System). In such a system, the fuel to be finally supplied to the internal combustion engine 10 is the type of fuel selected by the user of the vehicle and the refueling at the time of refueling to be executed at the user's desired timing. The amount varies depending on the amount, the amount of fuel remaining in the fuel tank and the type thereof.

[Configuration of Variable Valve Mechanism of this Embodiment]
FIG. 2 is a diagram showing the configuration of the intake variable valve mechanism 34 provided in the system shown in FIG. Hereinafter, the intake variable valve mechanism 34 will be further described with reference to FIG. The exhaust variable valve mechanism 36 has substantially the same configuration as the intake variable valve mechanism 34, and therefore detailed illustration and description thereof will be omitted.

  As shown in FIG. 2, the internal combustion engine 10 includes two intake valves 30 per cylinder. The internal combustion engine 10 includes the four cylinders (# 1 to # 4) as described above, and the explosion stroke is performed in the order of # 1 → # 3 → # 4 → # 2. The intake variable valve mechanism 34 includes two devices, that is, an intake variable valve mechanism 34A and an intake variable valve mechanism 34B. The intake variable valve mechanism 34A drives the intake valves 30 provided in the # 2 and # 3 cylinders, and the intake variable valve mechanism 34B drives the intake valves 30 provided in the # 1 and # 4 cylinders.

  The intake variable valve mechanism 34A includes an electric motor (hereinafter referred to as a motor) 50A as a drive source, a gear train 52A as a transmission mechanism that transmits the rotational motion of the motor 50A, and the rotational motion transmitted from the gear train. A camshaft 54A that converts the valve 30 into a linear opening / closing motion. Similarly, the intake variable valve mechanism 34B includes a motor 50B, a gear train 52B, and a camshaft 54B.

  The motors 50A and 50B are servo motors capable of controlling the rotation speed and the rotation amount. For example, a DC brushless motor or the like is preferably used as the motors 50A and 50B. The motors 50A and 50B incorporate rotation angle detection sensors such as a resolver and a rotary encoder for detecting the rotation position (rotation angle). The rotational speed and amount of rotation of the motors 50A and 50B are controlled by the ECU 40.

  A cam drive gear 56 that rotates integrally with the camshafts 54A and 54B and a cam 58 that also rotates integrally with the camshafts 54A and 54B are provided on the outer periphery of the camshafts 54A and 54B, respectively.

  The gear train 52A may be configured such that the rotation of the motor gear 62A attached to the output shaft 60 of the motor 50A causes the camshaft 54A to rotate at an equal speed via the intermediate gear 64A, with respect to the motor gear 62A. The cam drive gear 56 may be configured to increase or decrease speed. Similarly, the gear train 52B transmits the rotation of the motor gear 62B attached to the output shaft of the motor 50B to the cam drive gear 56 of the camshaft 54B via the intermediate gear 64B (not shown in FIG. 2).

  As shown in FIG. 2, the camshaft 54A is disposed above the intake valves 30 of the # 2 and # 3 cylinders, and the cams 58 provided on the camshaft 54A make the intake valves 30 of the # 2 and # 3 cylinders. It is opened and closed. The camshaft 54B is divided into two parts and is disposed on the upper part of the intake valves 30 of the # 1 and # 4 cylinders. The cam 58 provided on the camshaft 54B is used to intake the # 1 and # 4 cylinders. The valve 30 is driven to open and close. The camshaft 54B divided into two is connected via a connecting member inserted into the hollow camshaft 54A and is configured to rotate integrally.

  FIG. 3 is a schematic diagram showing how the intake valve 30 is driven by the cam 58. The cam 58 is formed as a kind of plate cam in which a nose 58a is formed by inflating a part of an arc-shaped base circle 58b coaxial with the camshafts 54A and 54B outward in the radial direction. The profile of the cam 58 is set so that a negative curvature does not occur over the entire circumference, that is, a convex curved surface is drawn outward in the radial direction.

  As shown in FIG. 2, each intake valve 30 includes a valve shaft 30a. Each cam 58 faces a valve lifter 66 provided at one end of the valve shaft 30 a of the intake valve 30. Each intake valve 30 is biased toward the cam 58 by a compression reaction force of a valve spring (not shown). When the base circle 58b of the cam 58 faces the valve lifter 66, the intake valve 30 is brought into close contact with the valve seat (not shown) of the intake port by the urging force of the valve spring, and the intake port is closed.

  When the rotational motion of the motors 50A and 50B is transmitted to the camshafts 54A and 54B via the gear trains 52A and 52B, the cam 58 rotates integrally with the camshafts 54A and 54B, and the nose 58a passes over the valve lifter 66. The valve lifter 66 is pushed down, and the intake valve 30 lifts (opens) against the urging force of the valve spring.

  3A and 3B show two drive modes of the cam 58. FIG. In the drive mode of the cam 58, the motors 50A and 50B are continuously rotated in one direction so that the cam 58 is at the maximum lift position as shown in FIG. Is a normal rotation drive mode in which the valve lifter 66) is continuously rotated beyond the position in contact with the valve lifter 66) in the normal rotation direction (the arrow direction in FIG. 3A), and the motor 50A before reaching the maximum lift position in the normal rotation drive mode. , And a swing drive mode in which the cam 58 is reciprocated as shown in FIG.

  In the normal rotation drive mode, the operating angle of the intake valve 30 is controlled by controlling the rotational speed of the cam 58. In the swing drive mode, the operating angle and lift amount of the intake valve 30 can be controlled by controlling the rotational speed of the cam 58 and the angle range in which the cam 58 swings. Thus, according to the intake variable valve operating mechanism 34, it is possible to drive the intake valve 30 with the optimum operating angle and lift amount (valve opening characteristic) according to the operating state.

  Further, according to the variable valve mechanism 34, during the lift operation, the rotational speed of the cam 58 is changed during the lift operation of the intake valve 30 regardless of whether in the forward drive mode or the swing operation mode. The lift speed of the intake valve 30 can be adjusted.

  FIG. 4 is a schematic diagram showing in detail two cams 58 provided on the camshaft 54A. As shown in FIG. 4, on the camshaft 54A, the cam 58 for driving the intake valve 30 for the # 2 cylinder and the cam 58 for driving the intake valve 30 for the # 3 cylinder are at an angular position of 180 °. Are spaced apart. In the four-cylinder internal combustion engine, the explosion strokes are performed in the order of # 1, # 3, # 4, and # 2 during the crank angle of 720 °. Therefore, the intake stroke of the # 2 cylinder and the # 3 cylinder is 360 ° of the crank angle. Done every time. In the intake variable valve mechanism 34A, the # 2 cylinder cam 58 and the # 3 cylinder cam 58 alternately drive the # 2 cylinder intake valve 30 and the # 3 cylinder intake valve 30 at every 360 ° crank angle. Then, the camshaft 54A is rotated or swung. Similarly, the camshaft 54B is provided with a cam 58 for driving the intake valves 30 of the # 1 cylinder and # 4 cylinder, and the intake variable valve mechanism 34B rotates or swings the camshaft 54B. Thus, the intake valve 30 of the # 1 cylinder and the intake valve 30 of the # 4 cylinder are driven.

[Intake valve slow-open control]
Next, the intake valve delay opening control will be described with reference to FIG.
When the internal combustion engine 10 is started in an extremely low temperature range, the injected fuel is less likely to atomize, and the injected fuel is likely to adhere to the wall surface of the intake port 16a and the wall surface of the combustion chamber 14. As a result, the fuel that does not contribute to the combustion of the injected fuel increases, and it becomes necessary to inject a larger amount of fuel than usual. Such a problem is not limited to when starting in an extremely low temperature range, but also when a fuel that hardly evaporates, such as alcohol fuel or gasoline fuel with a lot of heavy components, is used.

  Therefore, in the system of the present embodiment, when starting in an extremely low temperature range or when using high alcohol concentration fuel, the control for delaying the opening timing of the intake valve 30 from the intake top dead center, that is, “intake valve” "Slow opening control" is executed.

  FIG. 5 is a graph comparing the in-cylinder temperature and the valve passage flow rate in the intake stroke and the compression stroke between the intake valve timing in the normal time and the intake valve timing in the intake valve delay opening control. In the example shown in FIG. 5, the “normal intake valve timing” referred to for comparison opens at about 10 ° CA before intake top dead center and closes at about 30 ° CA after intake bottom dead center. It is considered as valve timing. On the other hand, as the “valve timing at the time of intake valve delay opening control”, the opening timing is retarded to about 60 ° CA after the intake top dead center, and the closing timing is set to the vicinity of the intake bottom dead center. The valve timing is taken as an example.

  From FIG. 5 (A), it can be seen that in the initial stage of the intake stroke at which the intake valve 30 starts to open, the decrease in the in-cylinder temperature is suppressed during the execution of the intake valve delay opening control compared to the normal time. . The following reasons are conceivable. That is, when the intake valve delay opening control is employed, the in-cylinder negative pressure is sufficiently increased during the negative valve overlap period until the intake valve 30 is opened. The difference between the internal pressure of the intake port 16a and the in-cylinder pressure increases. When the intake valve 30 is opened slowly, the piston speed near the opening timing increases. Due to these two factors, as shown in FIG. 5B, the valve passage flow rate when the intake valve 30 is opened increases. As a result, the friction loss when the intake air passes through the intake valve 30 increases, and the intake air is heated. Thereby, the fall of in-cylinder temperature is suppressed as mentioned above.

  In addition, when the intake valve delay opening control is executed, the actual compression ratio is improved by closing the intake valve 30 in the vicinity of the intake bottom dead center. For this reason, as shown in FIG. 5A, in the compression stroke, the in-cylinder temperature is maintained higher during execution of the intake valve retarded opening control than during normal operation. In addition, when the intake valve slow opening control is executed and the intake valve passage flow rate is increased over a certain period after the intake valve 30 is opened, fuel atomization is promoted.

  According to the intake valve slow-opening control described above, it is possible to improve the combustion by maintaining the in-cylinder temperature high and increasing the compression end temperature, and by the fuel atomization promoting effect by increasing the intake valve passage flow rate. It is possible to ensure good startability of the internal combustion engine 10 even when starting in an extremely low temperature range or when using a fuel with a high alcohol concentration.

  FIG. 6 is a diagram for explaining a problem of intake valve delay opening control. As described above with reference to FIG. 5B, when the intake valve slow opening control is executed, the intake valve passing flow velocity when the intake valve 30 is opened becomes considerably large. As a result, the fuel accumulated in the umbrella portion of the intake valve 30, the wall surface of the intake port 16a, and the like is likely to flow into the cylinder vigorously on the flow of intake air. Further, at the initial stage of opening the intake valve 30, the lift amount of the intake valve 30 is very small. For this reason, the traveling direction of the fuel is a direction toward the spark plug 28 located at the center of the combustion chamber 14 as shown in FIG. As a result, the fuel directly hits the spark plug 28, and if such a state continues for a long time, a fuel fog occurs on the spark plug 28. In addition, the fuel injected into the intake port 16a vigorously reaches the periphery of the exhaust valve 32 together with the intake air, and adheres as so-called “cylinder wet” in the state of liquid droplets around the exhaust valve 32 and its periphery. End up.

[Characteristic Control of Intake Valve 30 in Embodiment 1]
FIG. 7 is a lift curve for explaining the control of the intake valve 30 which is characteristic in the first embodiment of the present invention. The two lift curves shown in FIG. 7 are respectively the timing (about 410 ° CA in FIG. 7) when the opening timing of the intake valve 30 is retarded from the intake top dead center (360 ° CA in FIG. 7). In addition, the closing timing of the intake valve 30 is about 10 ° CA (about 550 ° CA in FIG. 7) after the intake bottom dead center. That is, lift curves A and B shown in FIG. 7 both indicate lift curves when the intake valve delay opening control is executed.

  More specifically, the lift curve A represented by a thick curve in FIG. 7 is a lift curve that is referred to for comparison with the lift curve used in the present embodiment, and is different from the lift curve B of the present embodiment. It is a normal lift curve having a curve that is symmetrical with respect to the maximum lift position under the same operating angle condition. On the other hand, the lift curve B represented by a thin curve in FIG. 7 corresponds to the lift curve used in this embodiment.

  As shown in FIG. 7, the lift curve B of the present embodiment is a curve that reaches the maximum lift position earlier than the normal lift curve A that is symmetric in the longitudinal direction. More specifically, the lift curve B of the present embodiment is compared with a normal lift curve A that is symmetric in the longitudinal direction at the same crank angle, and a predetermined crank angle (near the maximum lift position) from the opening timing of the intake valve 30. The lift amount in the section up to is increased. In other words, the lift curve B indicates that the absolute value of the lift speed of the intake valve 30 in the first half section from the opening timing to the maximum lift position is the absolute value of the lift speed of the intake valve 30 in the second half section from the maximum lift position to the closing timing. Has been bigger than.

  In addition, the speed of the piston 12 is highest in the vicinity of 90 ° CA after the intake top dead center. Therefore, in the lift curve B of the present embodiment, the lift amount of the intake valve 30 is in the vicinity of 90 ° CA after the intake top dead center where the valve passage flow velocity is most likely to be highest when the speed of the piston 12 is highest. The maximum lift position is set.

  FIG. 8 is a diagram for explaining the effect of adopting the lift curve B shown in FIG. 7, and shows the relationship between the valve passage flow velocity of the intake valve 30 and the crank angle. The lift curves A and B shown in FIG. 7 both employ intake valve slow opening control, so that the intake valve passing flow velocity instantaneously increases when the intake valve 30 opens. This is because when the intake valve slow opening control is executed, as described above, the difference between the internal pressure of the intake port 16a and the in-cylinder pressure when the intake valve 30 is opened becomes sufficiently large.

  When the lift curve B (thin line) of the present embodiment is employed, the lift amount on the first half side from the maximum lift position is higher than the lift amount on the lift curve A that is symmetrical in the longitudinal direction. As shown in FIG. 2, in the initial stage of opening of the intake valve 30, the period during which the valve passage flow velocity shows the maximum flow velocity is shortened. Furthermore, the valve passage flow rate can be reduced by an area indicated by hatching in FIG.

  For this reason, according to the lift curve B of the present embodiment, the valve passage flow velocity is an excessive value while the effect of improving the instantaneous valve passage flow velocity in the initial valve opening stage of the intake valve 30 by the intake valve delay opening control is maintained. Can be shortened. Thereby, the flow of the intake air toward the spark plug 28 and the exhaust valve 32 can be reduced while maintaining the fuel atomization promoting effect satisfactorily. For this reason, it is possible to satisfactorily prevent fogging of the spark plug 28 while maintaining the fuel atomization promoting effect satisfactorily, and to reduce the cylinder wet amount favorably.

  In the lift curve B of the present embodiment, consideration is given to setting the lift curve so that the lift amount of the intake valve 30 becomes the maximum lift position in the vicinity of 90 ° CA after the intake top dead center. For this reason, the lift amount of the intake valve 30 can be effectively increased in the vicinity of 90 ° CA after the intake top dead center where the speed of passage of the valve 12 is most likely to become the highest as the speed of the piston 12 increases. Thus, it is possible to effectively shorten the period in which the valve passage flow rate shows an excessive value.

[Specific Processing in Embodiment 1]
FIG. 9 is a flowchart of a routine executed by the ECU 40 in the first embodiment in order to realize the above function. This routine is a routine that is started when the internal combustion engine 10 is started.

  In the routine shown in FIG. 9, first, the engine speed Ne and the engine coolant temperature are acquired (step 100). Next, it is determined whether or not it is during a cold start of the internal combustion engine 10 based on the acquired information such as the engine speed Ne and the engine coolant temperature (step 102).

  As a result, when it is determined that the internal combustion engine 10 is not cold-started, a lift curve that is symmetrical in the longitudinal direction with respect to the maximum lift position is selected as the lift cars of the intake valve 30 (step 104). More specifically, in this step 104, the lift curve is set such that the necessary intake air amount Ga can be obtained with such a longitudinally symmetrical lift curve selected.

  On the other hand, if it is determined in step 102 that the internal combustion engine 10 is in a cold start, that is, since the start is in an extremely low temperature range, the intake valve 30 is slowly opened to promote fuel atomization. When it can be determined that it is necessary to improve the intake air flow velocity or suppress the decrease in the in-cylinder temperature by the control, the lift speed in the first-half section as the lift curve of the intake valve 30 is based on the maximum lift position. A lift curve that is higher than the lift speed in this section is selected (step 106). More specifically, in this step 106, the lift curve is set such that the necessary intake air amount Ga can be obtained in a state where such lift curves having different lift speeds on the first half side and the second half side are selected. Is done.

  Next, the intake valve 30 is driven using the intake variable valve mechanism 34 so that the lift curve selected in the above step 104 or 106 is obtained (step 108). In addition, in the case of step 106 described above, by changing the rotational speed of the cam 58 during the lift operation of the intake valve 30, the lift speed of the intake valve 30 is changed between the first half side and the second half side based on the maximum lift position. Adjusted.

  According to the routine shown in FIG. 9 described above, when the internal combustion engine 10 is cold started, the lift curve in which the lift amount in the section from the opening timing of the intake valve 30 to a predetermined crank angle (near the maximum lift position) is increased. And the slow opening control of the intake valve 30 is executed. For this reason, by maintaining the effect of improving the instantaneous valve passage flow rate in the initial stage of opening the intake valve 30, the fogging of the spark plug 28 is improved while the effect of promoting atomization of fuel is maintained well. In addition, the cylinder wet amount can be satisfactorily reduced.

  By the way, in the routine shown in FIG. 9 according to the first embodiment described above, when the slow opening control of the intake valve 30 is performed during the cold start of the internal combustion engine 10, the lift speed on the first half side is based on the maximum lift position. A lift curve B that is higher than the lift speed on the side is selected. However, the operating condition for executing the slow opening control of the intake valve 30 while selecting such a lift curve B is not limited to the cold start of the internal combustion engine 10. That is, for example, whether or not the intake valve delay opening control is performed may be switched based on the property of the fuel. Specifically, when it is determined that fuel with a high alcohol concentration is used, or when it is determined that heavy fuel with poor evaporation characteristics is used, the intake valve that selects the lift curve B is selected. The slow opening control may be executed. Further, as long as it is based on the environmental temperature of the internal combustion engine 10, it is not limited to that based on the engine coolant temperature. For example, whether or not the intake valve slow-opening control in which the lift curve B is selected based on the outside air temperature is executed. May be switched.

  In the first embodiment described above, the “intake valve delay opening control means” in the first and third inventions is realized by the ECU 40 executing the processing of steps 102, 106, and 108, respectively. Yes.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to FIGS.
The system of the present embodiment can be realized by causing the ECU 40 to execute a routine shown in FIG. 11 described later instead of the routine shown in FIG. 9 using the hardware configuration shown in FIGS. is there.

  FIG. 10 is a diagram for explaining characteristic control in Embodiment 2 of the present invention. The system according to the present embodiment has a predetermined timing from the opening timing of the intake valve 30 in comparison with a normal lift curve that is symmetric with respect to the maximum lift position under the same operating angle condition when the intake valve slow opening control is executed. When the lift amount in the section up to the crank angle (near the maximum lift position) is increased, it is based on the environmental temperature of the internal combustion engine 10 or fuel volatility (heavy or light fuel components, alcohol concentration, etc.) Thus, the lift amount in the predetermined section is variable.

  As the environmental temperature (cooling water temperature, outside air temperature, etc.) of the internal combustion engine 10 becomes lower, the fuel is less likely to volatilize. Further, when an alcohol fuel such as ethanol is used, the higher the alcohol concentration, the less likely the fuel will volatilize. Furthermore, as the heavy component contained in the fuel increases, the fuel is less likely to volatilize. Therefore, in the present embodiment, as shown in FIG. 10, the lift amount in the predetermined section becomes larger as the condition that the volatility of the fuel used becomes worse or the environmental temperature of the internal combustion engine 10 becomes lower. I was able to increase it. Specifically, the lift amount in the predetermined section can be further increased by increasing the lift speed on the first half side based on the maximum lift position.

FIG. 11 is a flowchart of a routine executed by the ECU 40 in the second embodiment in order to realize the above function.
In the routine shown in FIG. 11, first, it is determined whether or not an execution condition for intake valve delay opening control is satisfied (step 200). More specifically, the execution condition of the intake valve slow-opening control is highly demanded to promote atomization of fuel, such as when the internal combustion engine 10 is started in an extremely low temperature range or when high alcohol concentration fuel is used. Applicable when under operating conditions.

  If it is determined in step 200 that the intake valve delay opening control execution condition is satisfied, engine coolant temperature and alcohol concentration information is acquired (step 202). More specifically, the engine coolant temperature can be acquired using the coolant temperature sensor 46. Further, the alcohol concentration information can be acquired by, for example, a fuel property determination method using an air-fuel ratio feedback correction amount.

  Next, based on the acquired engine coolant temperature and alcohol concentration information, the first half and the second half lift speeds based on the maximum lift position when the intake valve slow opening control is executed are determined (step). 204). In order to determine such lift speed, the ECU 40 has a relationship as shown in FIG. 12, that is, each of the lift speeds on the first half side (opening side (lifting side)) and the second half side (closing side (downward side)). And a map that defines the relationship between the engine coolant temperature and the ethanol concentration.

  In the relationship shown in FIG. 12, the lift speed on the opening side (first half side) is set such that the lift speed increases as the engine coolant temperature decreases or as the ethanol concentration increases. . On the contrary, the lift speed on the closing side (second half side) is set so that the lift speed decreases as the engine coolant temperature decreases or as the ethanol concentration increases. In the relationship shown in FIG. 12, the maximum lift speed on the opening side (first half side) is set to be a speed at which the maximum lift position of the lift amount is in the vicinity of 90 ° CA after the intake top dead center. Has been. Here, the cooling water temperature and the ethanol concentration (alcohol concentration) are taken as an example, but the parameters for determining the lift speed are not these parameters, but the outside air temperature and fuel as described above are also used. May be a component.

  Next, the intake valve 30 is driven using the intake variable valve mechanism 34 so that a lift curve reflecting the lift speed determined in step 204 is obtained (step 206).

  According to the routine shown in FIG. 11 described above, the predetermined amount of time from the opening timing of the intake valve 30 is increased as the volatility of the fuel used becomes worse, or as the environmental temperature of the internal combustion engine 10 becomes lower. The lift amount in the section can be further increased. When starting up in extremely low temperature conditions or under extremely low volatility of the fuel used, by sufficiently increasing the lift speed on the first half side, it is possible to sufficiently increase the fogging of the spark plug 28 and the increase in the cylinder wet amount. There is a demand to prevent. On the other hand, when the degree of fuel volatility is low, or when starting the engine where it can be said that the temperature conditions are relatively harsh, the intake flow rate is improved by making the most of the original effect of the intake valve slow-open control. There is a demand to obtain sufficient fuel atomization promoting effect.

  According to the control of the above routine, the fuel is less likely to volatilize, so that the fuel is more likely to accumulate in the umbrella portion of the intake valve 30 or the like, or under such circumstances that such fuel does not accumulate relatively. Even in such a situation that the fuel does not sufficiently evaporate and flows into the cylinder, the fuel atomization promoting effect and the cylinder are determined based on the volatility of the fuel used and the environmental temperature of the internal combustion engine 10. It is possible to achieve a good balance with the effect of reducing the wet amount.

  In the second embodiment described above, the “information acquisition means” in the second and fourth aspects of the present invention is realized by the ECU 40 executing the process of step 202 described above.

  In the first and second embodiments described above, an example in which the present invention is applied to the port injection internal combustion engine 10 is described. However, the internal combustion engine that is the subject of the present invention is a port injection internal combustion engine. For example, an in-cylinder direct injection internal combustion engine may be used. That is, even in an internal combustion engine of the type in which fuel is directly injected into the cylinder, when the valve passage flow rate becomes excessive due to intake valve delay opening control, the fuel injected into the cylinder flows into the flow of intake air at a high flow rate. It is assumed that the cylinder wet amount increases due to the flow to the cylinder wall surface. According to the present invention, such an increase in the cylinder wet amount can be suppressed.

  In the first and second embodiments described above, the intake variable valve mechanism 34 is used in which the cam 58 that drives the intake valve 30 is electrically driven by the motor 50 around the camshaft 54. However, the variable valve mechanism applied to the present invention is not limited to the above-described mechanism as long as the opening timing and lift speed of the intake valve can be changed. An electromagnetically driven valve that opens and closes the intake valve may be used. Further, the change of the lift speed is not limited to the change of the rotational speed of the cam or the adjustment of the electromagnetic force. For example, a plurality of intake cams may be provided and the cam to be used may be switched.

It is a figure for demonstrating the structure of the internal combustion engine of Embodiment 1 of this invention. It is a figure which shows the structure of the intake variable valve mechanism with which the system shown in FIG. 1 is provided. It is a schematic diagram which shows a mode that an intake valve is driven with a cam. It is a schematic diagram which shows in detail the two cams provided in the cam shaft. FIG. 6 is a diagram comparing the in-cylinder temperature and the valve passage flow rate in the intake stroke and the compression stroke between the intake valve timing at the normal time and the intake valve timing at the time of intake valve delay opening control. It is a figure for demonstrating the subject of intake valve late opening control. It is a lift curve for demonstrating characteristic intake valve control in Embodiment 1 of this invention. It is a figure for demonstrating the effect which employ | adopted the lift curve B shown in FIG. It is a flowchart of the routine performed in Embodiment 1 of the present invention. It is a figure for demonstrating the characteristic control in Embodiment 2 of this invention. It is a flowchart of the routine performed in Embodiment 2 of this invention. It is a figure showing the relationship of the lift speed determination map referred during execution of the routine shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 12 Piston 14 Combustion chamber 16 Intake passage 16a Intake port 18 Exhaust passage 26 Fuel injection valve 28 Spark plug 30 Intake valve 32 Exhaust valve 34 Intake variable valve mechanism 40 ECU (Electronic Control Unit)
42 Crank angle sensor 44 Accelerator opening sensor 46 Cooling water temperature sensor 48 Outside air temperature sensor 50A, 50B Motor 54A, 54B Camshaft 58 Cam

Claims (6)

A variable valve mechanism that can change at least the opening timing and lift speed of the intake valve;
An intake valve delay opening control means for controlling the variable valve mechanism to perform an intake valve delay opening control for retarding the opening timing of the intake valve from the intake top dead center;
The intake valve slow opening control means has a higher lift amount in a section from the opening timing of the intake valve to a predetermined crank angle, compared to a lift curve that is symmetric with respect to the maximum lift position under the same operating angle condition. A control apparatus for an internal combustion engine comprising a variable valve mechanism that controls an intake valve. Further comprising information acquisition means for acquiring environmental temperature information of the internal combustion engine and / or information on fuel volatility;
The intake valve slow opening control means variably changes the lift amount in a section from the opening timing of the intake valve to the predetermined crank angle based on the environmental temperature information of the internal combustion engine and the information on fuel volatility. The control device for an internal combustion engine comprising the variable valve mechanism according to claim 1. A variable valve mechanism that can change at least the opening timing and lift speed of the intake valve;
An intake valve delay opening control means for controlling the variable valve mechanism to perform an intake valve delay opening control for retarding the opening timing of the intake valve from the intake top dead center;
The intake valve slow-opening control means is configured such that the absolute value of the lift speed in at least a part of the first half section from the maximum lift position is the absolute value of the lift speed in the second half section from the maximum lift position. An internal combustion engine control device comprising a variable valve mechanism that controls an intake valve so as to be larger than a value. Further comprising information acquisition means for acquiring environmental temperature information of the internal combustion engine and / or information on fuel volatility;
The intake valve slow-opening control means is based on the environmental temperature information of the internal combustion engine and / or the information on fuel volatility, and the at least a part of the first half of the section from the maximum lift position in the section. 2. A control apparatus for an internal combustion engine comprising a variable valve mechanism according to claim 1, wherein the lift speed is variably controlled.   5. The intake valve according to claim 1, wherein the intake valve slow-opening control means controls the intake valve so that the maximum lift position arrives in the vicinity of 90 ° CA after the intake top dead center. A control device for an internal combustion engine including a variable valve mechanism.   The internal combustion engine having a variable valve mechanism according to any one of claims 1 to 5, wherein the variable valve mechanism is a mechanism capable of electrically rotating a cam for driving an intake valve around a camshaft. Control device.

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